Risk factors for toxicity
Warfarin is a substrate for the cytochrome P450 drug metabolising system enzyme, CYP2C9. People taking drugs that inhibit CYP2C9 are more susceptible to toxic effects of warfarin (overanticoagulation) because enzyme inhibition can raise serum warfarin concentration and prolong its half-life1. However, this effect is more relevant in the context of its therapeutic interactions than in poisoning.